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Table 4 Power calculation for changes in practice for various assumptions of % with practice pre-intervention – p1(20–60%), p2 (30–90%), assuming 80% power at 5% level of statistical significance (2-sided test), for sizes of effect ≤ 2 and for cluster size six (numbers of annual live births per hospital)

From: The BLISS cluster randomised controlled trial of the effect of 'active dissemination of information' on standards of care for premature babies in England (BEADI) study protocol [ISRCTN89683698]

ICC assumption required for 780 babies

p 1

P 2

 

30

35

40

45

50

55

60

65

70

75

80

85

90

 

60

        

0.02

0.31

    

55

        

0.28

     

50

       

0.26

      

45

      

0.25

0.6

      

40

     

0.25

0.6

       

35

   

0.01

0.26

0.6

        

30

  

0.02

0.28

          

25

 

0.04

0.31

           

20

0.06

0.36

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